Antibodies are known to have powerful therapeutic effects and are currently used for the treatment of a range of diseases including cancer, autoimmune diseases, cardiovascular disease, and transplant rejection. Traditionally, therapeutic antibodies are produced by recombinant technology, formulated and then administered to patients in need of antibody therapy. However, antibody production and formulation is highly expensive. In addition, many antibodies only have a very short half-life in vivo and therefore, may not reach their target antigen or target tissue before being degraded. To achieve desired efficacy, antibody therapy often requires high doses and frequent administration.
Gene therapy and genetic vaccination, also known as DNA vaccination, provide alternative approaches for delivery of large amounts of antibodies in vivo. However, the use of DNA as an agent in gene therapy and genetic vaccination may cause some safety concerns. For example, DNA is degraded slowly in the bloodstream. Formation of anti-DNA antibodies may occur (Gilkeson et al., J. Clin. Invest. 1995, 95: 1398-1402). The possible persistence of (foreign) DNA in the organism can thus lead to a hyperactivation of the immune system, which was known to result in splenomegaly in mice (Montheith et al., Anticancer Drug Res. 1997, 12(5): 421-432). Furthermore, DNA integration can cause mutations in the host genome by interrupting an intact gene.